mixture of silex; and both these concretions and the flinty strata appear to have originated during the fluid state of the matrix in which we find them imbedded, and to have proceeded with it through a nearly contemporaneous process of consolidation; the separation of the siliceous from the calcareous ingredients having been modified by attractions which drew to certain centres the particles of the siliceous nodules as they were in the act of separation from the original compound mass, and the distances of the siliceous strata having probably been regulated by the intervals of precipitation of the matter from which they were derived, each new mass as it was discharged forming a bed of pulpy fluid at the bottom of the then existing ocean, which being more recent than the bed produced by the last preceding precipitate, would rest on it as a foundation similar in substance to itself, but of which the consolidation was sufficiently advanced to prevent the ingredients of the last deposit from penetrating or disturbing the productions of that which preceded it.
The result of a succession of such deposits as are here supposed would be the accumulation of a formation of homogeneous strata, each containing in a fossil state such organic remains as happened to be entangled in the successive precipitates. The identity of these remains in that immense succession of beds which constitutes the mass of the chalk formation, is consistent with the identity of the matrix containing them; there being no reason to believe in any change of circumstances in the then existing condition of our globe, from the commencement to the completion of the deposition of the beds of chalk, since we find no admixture of sand or pebbles (the wreck of older strata), nor any symptom of interruption or irregularity in the processes from which has resulted that enormous
